1. Field of the Invention
The present invention is broadly concerned with an improved roof covering system. More particularly it is concerned with a system securing joint covers to the joint areas of adjacent roof panels in a weathertight relationship without the use of exposed fasteners while preventing longitudinal movement between the joints and covers.
2. Description of the Prior Art
Prior art metal roof panel attachment systems typically include a plurality of sheet metal panels mounted in overlapping relationship and having adjacent longitudinal margins with a joint area therebetween. Thermal expansion and contraction of the panels permit water, snow or ice to enter any exposed, unprotected joint areas, seep beneath the panels, and eventually cause damage to the underlying roof structure. Points where the panels are fastened to the roof structure also present areas vulnerable to moisture entry and consequent damage.
Previous systems have addressed these problems by fastening the panels to the roof with a bracket or batten structure mounted within the joint area and providing a cover which extends over the longitudinal margins of the adjacent panels and the interjacent joint areas. Such previous systems employ joint covers which are held in place by friction fit of the cover and battens and thus are free to expand and contract longitudinally in response to changes in the ambient temperature.
However, the absence of a securing point on each cover section limits the number of cover sections that can be safely employed in a single run to provide a roof having sufficient strength and uplift rating. On large areas where two or more cover sections are joined end-to-end, movement from thermal expansion and contraction can cause the sections to work apart at the end seams unless an exposed fastener is employed. The strength of such roof panel attachment systems is not uniform as the securing forces are focused on individual fasteners. Expansion and contraction forces are likewise focused on these fasteners, which must bend to absorb thermal movement of the roof system.
Other prior attachment systems have employed wood as a batten support. Since the configuration of the available wood stocks is rectilinear, the joint cover design in such systems is limited to a specific rectangular or trapezoidal geometry determined by the shape of the stock. The use of curved forms is effectively precluded. In addition, where rectilinear forms are employed, crimping machinery is required at the job site.